package wshandler

import (
	"context"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"sync"
	"time"

	"go.mongodb.org/mongo-driver/bson/primitive"
	"repositories.action2quare.com/ayo/gocommon"
	"repositories.action2quare.com/ayo/gocommon/flagx"
	"repositories.action2quare.com/ayo/gocommon/logger"

	"github.com/go-redis/redis/v8"
	"github.com/gorilla/websocket"
)

var noSessionFlag = flagx.Bool("nosession", false, "nosession=[true|false]")

type wsconn struct {
	*websocket.Conn
	sender *Sender
}

type UpstreamMessage struct {
	Alias  string
	Accid  primitive.ObjectID
	Target string
	Body   []byte
	Tag    []string
}

type DownstreamMessage struct {
	Alias string   `json:",omitempty"`
	Body  string   `json:",omitempty"`
	Tag   []string `json:",omitempty"`
}

type commandType string

const (
	commandType_JoinRoom     = commandType("join_room")
	commandType_LeaveRoom    = commandType("leave_room")
	commandType_WriteControl = commandType("write_control")
)

type commandMessage struct {
	Cmd  commandType
	Args []any
}

type WebSocketMessageType int

const (
	TextMessage   = WebSocketMessageType(websocket.TextMessage)
	BinaryMessage = WebSocketMessageType(websocket.BinaryMessage)
	CloseMessage  = WebSocketMessageType(websocket.CloseMessage)
	PingMessage   = WebSocketMessageType(websocket.PingMessage)
	PongMessage   = WebSocketMessageType(websocket.PongMessage)
	Connected     = WebSocketMessageType(100)
	Disconnected  = WebSocketMessageType(101)
)

type Sender struct {
	Region string
	Accid  primitive.ObjectID
	Alias  string
}

type WebSocketMessageReceiver func(sender *Sender, messageType WebSocketMessageType, body io.Reader)

type subhandler struct {
	authCache         *gocommon.AuthCollection
	redisMsgChanName  string
	redisCmdChanName  string
	redisSync         *redis.Client
	connInOutChan     chan *wsconn
	deliveryChan      chan any
	localDeliveryChan chan any
	callReceiver      WebSocketMessageReceiver
	connWaitGroup     sync.WaitGroup
	region            string
}

// WebsocketHandler  :
type WebsocketHandler struct {
	authCaches    map[string]*subhandler
	RedisSync     *redis.Client
	receiverChain map[string][]WebSocketMessageReceiver
}

type wsConfig struct {
	SyncPipeline string `json:"ws_sync_pipeline"`
}

func NewWebsocketHandler(authglobal gocommon.AuthCollectionGlobal) (wsh *WebsocketHandler) {
	var config wsConfig
	gocommon.LoadConfig(&config)

	redisSync, err := gocommon.NewRedisClient(config.SyncPipeline, 0)
	if err != nil {
		panic(err)
	}

	// decoder := func(r io.Reader) *T {
	// 	if r == nil {
	// 		// 접속이 끊겼을 때.
	// 		return nil
	// 	}
	// 	var m T
	// 	dec := json.NewDecoder(r)
	// 	if err := dec.Decode(&m); err != nil {
	// 		logger.Println(err)
	// 	}

	// 	// decoding 실패하더라도 빈 *T를 내보냄
	// 	return &m
	// }

	authCaches := make(map[string]*subhandler)
	for _, region := range authglobal.Regions() {
		sh := &subhandler{
			authCache:         authglobal.Get(region),
			redisMsgChanName:  fmt.Sprintf("_wsh_msg_%s", region),
			redisCmdChanName:  fmt.Sprintf("_wsh_cmd_%s", region),
			redisSync:         redisSync,
			connInOutChan:     make(chan *wsconn),
			deliveryChan:      make(chan any, 1000),
			localDeliveryChan: make(chan any, 100),
			region:            region,
		}

		authCaches[region] = sh
	}

	return &WebsocketHandler{
		authCaches:    authCaches,
		RedisSync:     redisSync,
		receiverChain: make(map[string][]WebSocketMessageReceiver),
	}
}

func (ws *WebsocketHandler) RegisterReceiver(region string, receiver WebSocketMessageReceiver) {
	ws.receiverChain[region] = append(ws.receiverChain[region], receiver)
}

func (ws *WebsocketHandler) Start(ctx context.Context) {
	for region, sh := range ws.authCaches {
		chain := ws.receiverChain[region]
		if len(chain) == 0 {
			sh.callReceiver = func(sender *Sender, messageType WebSocketMessageType, body io.Reader) {}
		} else if len(chain) == 1 {
			sh.callReceiver = chain[0]
		} else {
			sh.callReceiver = func(sender *Sender, messageType WebSocketMessageType, body io.Reader) {
				for _, r := range chain {
					r(sender, messageType, body)
				}
			}
		}

		go sh.mainLoop(ctx)
	}
}

func (ws *WebsocketHandler) Cleanup() {
	for _, sh := range ws.authCaches {
		sh.connWaitGroup.Wait()
	}
}

func (ws *WebsocketHandler) RegisterHandlers(serveMux *http.ServeMux, prefix string) error {
	for region, sh := range ws.authCaches {
		if region == "default" {
			region = ""
		}
		url := gocommon.MakeHttpHandlerPattern(prefix, region, "ws")
		if *noSessionFlag {
			serveMux.HandleFunc(url, sh.upgrade_nosession)
		} else {
			serveMux.HandleFunc(url, sh.upgrade)
		}
	}

	return nil
}

func (ws *WebsocketHandler) GetState(region string, accid primitive.ObjectID) string {
	state, err := ws.RedisSync.Get(context.Background(), accid.Hex()).Result()
	if err == redis.Nil {
		return ""
	}
	return state
}

func (ws *WebsocketHandler) SetState(region string, accid primitive.ObjectID, state string) {
	ws.RedisSync.SetArgs(context.Background(), accid.Hex(), state, redis.SetArgs{Mode: "XX"}).Result()
}

func (ws *WebsocketHandler) SendUpstreamMessage(region string, msg *UpstreamMessage) {
	sh := ws.authCaches[region]
	if sh != nil {
		sh.localDeliveryChan <- msg
	}
}

func (ws *WebsocketHandler) SendCloseMessage(region string, target string, text string) {
	sh := ws.authCaches[region]
	if sh != nil {
		sh.localDeliveryChan <- &commandMessage{
			Cmd: commandType_WriteControl,
			Args: []any{
				target,
				int(websocket.CloseMessage),
				websocket.FormatCloseMessage(websocket.CloseNormalClosure, text),
			},
		}
	}
}

func (ws *WebsocketHandler) EnterRoom(region string, room string, accid primitive.ObjectID) {
	sh := ws.authCaches[region]
	if sh != nil {
		sh.localDeliveryChan <- &commandMessage{
			Cmd:  commandType_JoinRoom,
			Args: []any{room, accid},
		}
	}
}

func (ws *WebsocketHandler) LeaveRoom(region string, room string, accid primitive.ObjectID) {
	sh := ws.authCaches[region]
	if sh != nil {
		sh.localDeliveryChan <- &commandMessage{
			Cmd:  commandType_LeaveRoom,
			Args: []any{room, accid},
		}
	}
}

func (sh *subhandler) mainLoop(ctx context.Context) {
	defer func() {
		s := recover()
		if s != nil {
			logger.Error(s)
		}
	}()

	// redis channel에서 유저가 보낸 메시지를 읽는 go rountine
	go func() {
		var pubsub *redis.PubSub
		for {
			if pubsub == nil {
				pubsub = sh.redisSync.Subscribe(ctx, sh.redisMsgChanName, sh.redisCmdChanName)
			}

			raw, err := pubsub.ReceiveMessage(ctx)
			if err == nil {
				if raw.Channel == sh.redisMsgChanName {
					var msg UpstreamMessage
					if err := json.Unmarshal([]byte(raw.Payload), &msg); err == nil {
						sh.deliveryChan <- &msg
					} else {
						logger.Println("decode UpstreamMessage failed :", err)
					}
				} else if raw.Channel == sh.redisCmdChanName {
					var cmd commandMessage
					if err := json.Unmarshal([]byte(raw.Payload), &cmd); err == nil {
						sh.deliveryChan <- &cmd
					} else {
						logger.Println("decode UpstreamMessage failed :", err)
					}
				}
			} else {
				logger.Println("pubsub.ReceiveMessage failed :", err)
				pubsub.Close()
				pubsub = nil

				if ctx.Err() != nil {
					break
				}
			}
		}
	}()

	entireConns := make(map[string]*wsconn)
	rooms := make(map[string]*room)
	findRoom := func(name string, create bool) *room {
		room := rooms[name]
		if room == nil && create {
			room = makeRoom(name)
			rooms[name] = room
			room.start(ctx)
		}
		return room
	}

	// 유저에게서 온 메세지, 소켓 연결/해체 처리
	for {
		select {
		case usermsg := <-sh.localDeliveryChan:
			// 로컬에 connection이 있는지 먼저 확인해 보기 위한 채널
			// 없으면 publish한다.
			switch usermsg := usermsg.(type) {
			case *UpstreamMessage:
				target := usermsg.Target
				if target[0] == '@' {
					accid := target[1:]
					conn := entireConns[accid]
					if conn != nil {
						// 이 경우 아니면 publish 해야 함
						conn.WriteMessage(websocket.TextMessage, usermsg.Body)
						break
					}
				}
				if bt, err := json.Marshal(usermsg); err == nil {
					sh.redisSync.Publish(context.Background(), sh.redisMsgChanName, bt).Result()
				}

			case *commandMessage:
				if usermsg.Cmd == commandType_JoinRoom && len(usermsg.Args) == 2 {
					roomName := usermsg.Args[0].(string)
					accid := usermsg.Args[1].(primitive.ObjectID)
					conn := entireConns[accid.Hex()]
					if conn != nil {
						findRoom(roomName, true).in(conn)
						break
					}
				} else if usermsg.Cmd == commandType_LeaveRoom && len(usermsg.Args) == 2 {
					roomName := usermsg.Args[0].(string)
					accid := usermsg.Args[1].(primitive.ObjectID)
					conn := entireConns[accid.Hex()]
					if conn != nil {
						if room := findRoom(roomName, false); room != nil {
							room.out(conn)
							break
						}
					}
				} else if usermsg.Cmd == commandType_WriteControl && len(usermsg.Args) == 2 {
					accid := usermsg.Args[0].(string)
					conn := entireConns[accid]
					if conn != nil {
						conn.WriteControl(usermsg.Args[1].(int), usermsg.Args[2].([]byte), time.Time{})
						break
					}
				}

				// 위에서 break 안걸리면 나한테 없으므로 publish를 해야 함. 그러면 다른 호스트가 deliveryChan으로 받는다
				if bt, err := json.Marshal(usermsg); err == nil {
					sh.redisSync.Publish(context.Background(), sh.redisCmdChanName, bt).Result()
				}
			}

		case usermsg := <-sh.deliveryChan:
			switch usermsg := usermsg.(type) {
			case *UpstreamMessage:
				target := usermsg.Target
				if target[0] == '#' {
					// 룸에 브로드캐스팅
					roomName := target[1:]
					if room := findRoom(roomName, false); room != nil {
						room.broadcast(usermsg)
					}
				} else if target[0] == '@' {
					accid := target[1:]
					conn := entireConns[accid]
					if conn != nil {
						conn.WriteMessage(websocket.TextMessage, usermsg.Body)
					}
				}

			case *commandMessage:
				if usermsg.Cmd == commandType_JoinRoom && len(usermsg.Args) == 2 {
					roomName := usermsg.Args[0].(string)
					accid := usermsg.Args[1].(primitive.ObjectID)
					conn := entireConns[accid.Hex()]
					if conn != nil {
						findRoom(roomName, true).in(conn)
					}
				} else if usermsg.Cmd == commandType_LeaveRoom && len(usermsg.Args) == 2 {
					roomName := usermsg.Args[0].(string)
					accid := usermsg.Args[1].(primitive.ObjectID)
					conn := entireConns[accid.Hex()]
					if conn != nil {
						if room := findRoom(roomName, false); room != nil {
							room.out(conn)
						}
					}
				}

			default:
				logger.Println("usermsg is unknown type")
			}

		case c := <-sh.connInOutChan:
			if c.Conn == nil {
				delete(entireConns, c.sender.Accid.Hex())
				for _, room := range rooms {
					room.out(c)
				}
				sh.callReceiver(c.sender, Disconnected, nil)
			} else {
				entireConns[c.sender.Accid.Hex()] = c
				sh.callReceiver(c.sender, Connected, nil)
			}
		}
	}
}

func upgrade_core(sh *subhandler, conn *websocket.Conn, accid primitive.ObjectID, alias string) {
	newconn := &wsconn{
		Conn: conn,
		sender: &Sender{
			Region: sh.region,
			Alias:  alias,
			Accid:  accid,
		},
	}
	sh.connInOutChan <- newconn

	sh.connWaitGroup.Add(1)
	go func(c *wsconn, accid primitive.ObjectID, deliveryChan chan<- any) {
		sh.redisSync.Set(context.Background(), accid.Hex(), "online", 0)
		for {
			messageType, r, err := c.NextReader()
			if err != nil {
				c.Close()
				break
			}

			if messageType == websocket.CloseMessage {
				sh.callReceiver(c.sender, CloseMessage, r)
				break
			}

			if messageType == websocket.TextMessage {
				// 유저가 직접 보낸 메시지
				sh.callReceiver(c.sender, TextMessage, r)
			} else if messageType == websocket.BinaryMessage {
				sh.callReceiver(c.sender, BinaryMessage, r)
			}
		}
		sh.redisSync.Del(context.Background(), accid.Hex())
		sh.connWaitGroup.Done()

		c.Conn = nil
		sh.connInOutChan <- c
	}(newconn, accid, sh.deliveryChan)
}

func (sh *subhandler) upgrade_nosession(w http.ResponseWriter, r *http.Request) {
	// 클라이언트 접속
	defer func() {
		s := recover()
		if s != nil {
			logger.Error(s)
		}
		io.Copy(io.Discard, r.Body)
		r.Body.Close()
	}()

	auth := strings.Split(r.Header.Get("Authorization"), " ")
	if len(auth) != 2 {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	if auth[0] != "Editor" {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	temp, err := hex.DecodeString(auth[1])
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	if len(temp) != len(primitive.NilObjectID) {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	raw := (*[12]byte)(temp)
	accid := primitive.ObjectID(*raw)

	var upgrader = websocket.Upgrader{} // use default options
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		return
	}

	var alias string
	if v := r.Header.Get("AS-X-ALIAS"); len(v) > 0 {
		alias = v
	} else {
		alias = accid.Hex()
	}

	upgrade_core(sh, conn, accid, alias)
}

func (sh *subhandler) upgrade(w http.ResponseWriter, r *http.Request) {
	// 클라이언트 접속
	defer func() {
		s := recover()
		if s != nil {
			logger.Error(s)
		}
		io.Copy(io.Discard, r.Body)
		r.Body.Close()
	}()

	sk := r.Header.Get("AS-X-SESSION")
	auth := strings.Split(r.Header.Get("Authorization"), " ")
	if len(auth) != 2 {
		//TODO : 클라이언트는 BadRequest를 받으면 로그인 화면으로 돌아가야 한다.
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	authtoken := auth[1]

	accid, success := sh.authCache.IsValid(sk, authtoken)
	if !success {
		w.WriteHeader(http.StatusUnauthorized)
		return
	}

	var upgrader = websocket.Upgrader{} // use default options
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		return
	}

	var alias string
	if v := r.Header.Get("AS-X-ALIAS"); len(v) > 0 {
		alias = v
	} else {
		alias = accid.Hex()
	}

	upgrade_core(sh, conn, accid, alias)
}